The evidence to date on umbralisib for the treatment of refractory marginal zone lymphoma and follicular lymphoma.

INTRODUCTION

Between 2014 and 2018 The United States Food and Drug Administration granted approvals for three small molecule inhibitors of phosphoinositide 3-kinases (PI3Ks) as monotherapy for follicular lymphoma relapsed after at least 2 prior therapies. Idelalisib, copanlisib, and duvelisib each showed similar overall response rate and progression-free survival efficacy along with significant toxicity in separate phase II single-arm studies. Umbralisib, as the 4th iteration in this PI3K-inhibitor class for relapsed/refractory indolent B-cell lymphoma (iB-NHL), appears comparably active but may have improved tolerability.

AREAS COVERED: We review the use and limitations of PI3K-inhibitors for iB-NHL and discuss the development of and clinical results for umbralisib. Efficacy data are contextualized alongside other PI3K-inihibitors within the limitations of published single-arm studies. We compare and contrast available safety data, covering the off-target inhibition by umbralisib of casein kinase 1ε that is thought to contribute to a more favorable immune-mediated toxicity profile.

EXPERT OPINION: Though a late-comer to the PI3K-inihibitor party in iB-NHL, umbralisib may carve out an important role in treatment algorithms. Umbralisib's apparently superior safety needs to be confirmed in real-world and, ideally, comparative studies but stands to make it an attractive option in patients who are frail and/or seek treatments more compatible with remote management.